1. Technical Field
The present invention relates generally to rope drives working with high-strength fiber ropes such as crane hoists, boom adjustment gear, trolley traveling gear, etc. The invention in this respect in particular applies to hoist drums for the rope hoist winch of such a fiber rope drive having a groove drum jacket body which is provided with grooving at the peripheral side and having two guard plates adjacent to the drum jacket body at the end sides. The invention further relates to a rope pulley for such a fiber rope drive having a rotatably supported pulley body whose jacket surface has at least one rope groove.
2. Description of Related Art
An attempt has been being made for some time, in particular with cranes, to replace the customary heavy steel ropes with high-strength fiber ropes which consist of high-strength synthetic fibers such as aramid fibers (HMPA), aramid/carbon fiber composites, high-modulus polyethylene fibers (HMPE) or poly(p-phenylene-2,6-benzobisoxazole) fibers (PBO) or which at least comprise such fibers. Since the weight of the rope itself to be taken into account for the payload is smaller, the payload or the permitted lifting load can be increased due to the weight saving over steel ropes. Particularly with cranes having large lifting heights or boom or mast adjustment gear using pulley blocks of a high reeve number, considerable rope lengths and thus also a corresponding rope weight arise so that the weight reduction possible through high-strength fiber ropes is very advantageous.
However, the predisposition to wear and the secure recognition of the discard state have been problematic with such high-strength fiber ropes up to now. With the same rope diameter, steel ropes and high-strength fiber ropes of synthetic fibers have almost the same tensile strength; however, the steel wires have a significantly higher hardness than the fibers of the high-strength fiber ropes. A smaller transverse compressive stiffness of the high-strength fiber ropes results from this which are substantially softer and thereby not as resistant to wear as steel ropes if the rope is wound onto a drum or runs over rope pulleys, which can result in much higher wear at the high-strength fiber ropes.
In this respect, the region in which the hoist rope is wound onto or off the hoist drum in one or more layers as well as the region in which the rope runs around a rope pulley are particularly susceptible to wear. If the rope is coiled onto the drum jacket body of the hoist drum under load in the first layer, a relative movement results between the drum groove and the rope due to the stretching of the rope. A similar behavior results with a multilayer winding, with here rope then sliding on rope, which likewise results in friction and wear. A further wear region is the rope layer change when the rope is deflected by the drum guard plates.
To reduce friction wear, steel ropes are as a rule already greased in the rope arrangement, with a regular regreasing also being necessary in operation. A small coefficient of friction is obtained by this greasing and thus low wear in the winding of the ropes, especially the friction of the rope toward the drum body, the rope-on-rope friction and the friction on the running onto the guard plate or on the running onto the rope deflector is reduced. The same also applies to rope pulleys. A greased sliding of steel on steel thus has the great advantage of a low coefficient of friction and hereby low wear. This advantage of greasing cannot be used on the use of fiber ropes of plastic fibers in conjunction with hoist drums and rope pulleys.
With the hoist drum construction design for multilayer widening most frequently used at cranes, the drum jacket body is designed with a special grooving which allows a clean winding in a plurality of layers. The grooving in this respect has two pitch regions oppositely disposed viewed over the drum circumference and having a region of extent of around 90° in each case as well as two parallel regions which are likewise oppositely disposed and likewise have an extent of around 90° in each case. Each of the pitch regions in this respect provides a groove offset of around half a rope diameter.
Conventional hoist drums of the named kind are known, for example, from the document DE 101 32 611 A1 in which the pitch regions provided between the parallel regions have intercrossing grooves to allow a winding up of the rope both clockwise and counter clockwise. Furthermore, a hoist drum is known from DE 10 2005 004 816 A1 in which only the parallel region is actually provided with a grooving, while the pitch region is formed without grooves so that there the obliquely offset rope sections lie on a smooth, non-grooved jacket surface. Furthermore, DE 20 2008 011 359 U1 describes a hoist drum for a crane lifting gear, wherein an run-in guide is associated with the hoist drum in the run-in region of the rope and is formed from two oppositely disposed rollers while leaving a gap free whose gap width largely corresponds to the rope diameter. The named rope guide can be moved transversely, i.e. in parallel to the axis of rotation of the hoist drum, to ensure the desired winding quality. The previously addressed problems of the increased rope wear on the use of high-strength fiber ropes, however, remains unsolved in these already known hoist drums.